Higher organisms including humans have a gut immune function to prevent infections with pathogens such as bacteria, viruses and parasites, and production of various kinds of antibodies and cytokines are properly regulated in the gut. Particularly, immunoglobulin A (IgA) is a very important factor in gut immune system. In recent years, oral infections diseases tend to decrease as the living environment is cleaner. However, since secretion of IgA tends to decrease, it is feared that susceptibility of serious infection diseases increases with compromised gut immunity.
For a method of modulating gut immunity, International Patent Publication WO02/038146 discloses that trehalose, a kind of saccharide, has the regulatory effect of producing IgA and interferon-γ (IFN-γ) by acting on Peyer's patch cells. Japanese Patent Kokai 325555/2002 discloses that nigerooligosaccharides can prevent compromised immune function caused by nutritional disorders. However, these effects are insufficient. On the other hand, the cyclic tetrasaccharide disclosed in G. L. Cote, European Journal of Biochemistry, Vol. 226, 641-648 (1994) is not known for a function of modulating gut immunity at all.